What Does Petrol Do To A Diesel Engine?

Very often, the first question we are asked by a customer when we are attending a wrong fuel removal job is, “Will the engine be damaged by the petrol?” It’s the first thing that jumps into most people’s heads because it’s the nightmare scenario – having to replace the vehicle engine, especially if it’s a premium vehicle where replacement engines can cost many thousands of pounds to buy and fit. The reality is this; it is highly unlikely that there will be any permanent damage done to your diesel vehicle engine if you have simply filled up the fuel tank with petrol. Even if you have tried to start the car and have circulated petrol around the diesel engine components and fuel system, in the majority of cases the vehicle will be fine after a fuel drain and a fuel system flush through with fresh diesel fuel. Many wrong fuel websites warn against starting the vehicle which is what can put the panic into people’s minds, in truth it just makes the wrong fuel removal job a lot faster and easier, and so less costly, if the motorist hasn’t tried to start the engine.

Problems can start to occur if the vehicle has had a small amount of the wrong fuel added to the tank and then the motorist has tried to get away with it by topping up with diesel fuel to try to dilute the petrol. The car may run roughly with the contaminated fuel in the system and normal running may be restored once the petrol has worked it’s way out of the system. But, this is an enormously risky thing to do and the engine will in all likelihood, be damaged. This may not be immediately apparent, but over time the symptoms of damage will begin to show themselves.

Basically, petrol is a solvent and will damage the seals and other components in a diesel vehicle fuel system and engine which will cause them to gradually degrade and fail. Petrol also does not have the lubricating qualities of diesel fuel and so there will be a build up of friction between metal components that make up the sophisticated modern vehicle fuel system and they will wear out faster. This wear also introduces tiny metal particles into the fuel system which may get into the fuel injectors resulting in permanent damage and a very expensive repair job. A car that has been running for a period of time with contaminated fuel may develop the following problems:

  • Problems starting when warm
  • Excessive clouds of black smoke when accelerating
  • Rough idling when warm
  • Poor acceleration/reduced performance

If the fuel pump components are excessively worn then these problems will occur, eventually.

Having said all that, there’s really no need to panic if you’ve done the right thing and called Wrong Fuel Emergency out to assist as soon as you’ve realised that you’ve put in the wrong fuel. It’ll be much cheaper in the long run to address the problem straight away rather than try to get away with it.

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